Impact of Starter Fertilizer On Growth, Development and Yield Parameters of Corn.

ABSTRACT.  Starter fertilizer placed 5  5 cm below and to the side of planted corn seeds has been used by researchers and farmers to increase early-season growth and development.  Increased early season growth has occurred under cool and wet conditions; however, grain yield responses have been variable.  Our objective was to identify how starter fertilizer affected the progression of corn development and variability in growth.  A second objective was to identify the correlation of this early-season influence from starter fertilizer on final grain yield.  Treatments included three hybrids three populations (74,100, 88,900, and 103,700 seeds ha^-1), and with and without starter fertilizer (10.4 kg·ha^-1 N and 15.5 kg·ha^-1 P).  We measured stem diameter at soil surface until V6 and between the 7^th and 8^th nodes after V9, extended leaf plant height, and vegetative development on ten tagged plants at V2, V4, V6, V9, V15, and R2 during the 2011 growing season.  At each sampling date, identical measurements were collected on five plants in another row and then destructively sampled to attain plant and root dry weights.  Roots on destructively sampled plants were analyzed at V2 and V4 for root length, surface area, average diameter, number of tips and number of forks.  Per plant grain yield components and plot yield and grain moisture were measured.  Early-season growth progressed with starter fertilizer treatments; however, variability in early-season growth parameters such as height and stem diameter increased with starter fertilizer at the low plant density.  Starter fertilizer decreased days to silking and anthesis.  Increased variability in growth did not correlate to increased variability in grain yield components, and although starter fertilizer increased early season growth, yield was not different with starter fertilizer.